Effect of vaccination on COVID-19 mortality during omicron wave among highly marginalized mexican population.

Background: Social determinants have played a role in COVID-19 outcomes and vaccination has improved these and impacted on inflammatory response, we therefore sought to investigate the association between vaccination and inflammatory response with COVID-19 mortality in a Mexican population with high marginalization during the Omicron wave.

Methods: Prospective, longitudinal, single-center study in a setting of high marginalization conducted during the Omicron wave, from January to November 2022. Clinical and laboratory data were collected during admission and patients were followed until discharge or death. Patients were grouped according to outcome (survival and non-survival), and by complete (2 or more doses) and incomplete vaccination status for comparison.

Results: 118 patients were included, 54% (64/118) male, with a median age 63 years and 86% (102/118) with self-reported comorbidities. Mortality was 42%. 58% (68/118) had complete vaccination. There was a 64% risk reduction for all-cause in-hospital mortality of having complete vaccination, hazard ratio 0.36, (95% CI 0.18-0.71, p = 0.004) in the proportional hazards Cox regression test. Survivor group arrived earlier to medical care and had higher SpO2 on admission, and for inflammatory response, had lower levels of Neutrophil-to-lymphocyte ratio, C-reactive protein, and D-dimer at admission. In the longitudinal measurement, only D-dimer showed significant differences between groups according to survival.

Conclusion: In a highly marginalized Mexican population, complete vaccination has a protective effect against COVID-19 all-cause in-hospital mortality compared with incomplete or no vaccination. However, mortality in this population during the Omicron wave is high. Socio-economic inequalities may play an important role in COVID-19 outcomes.